1. Field of the Invention
The present invention relates to agricultural harvesters, and, more particularly, to choppers for agricultural harvesters.
2. Description of the Related Art
An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header, which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. A cleaning fan blows air through the sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a residue system, which may utilize a straw chopper to process the non-grain material and direct it out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
More particularly, a rotary threshing or separating system includes one or more rotors which can extend axially (front to rear) or transversely within the body of the combine, and which are partially or fully surrounded by a perforated concave. The crop material is threshed and separated by the rotation of the rotor within the concave. Coarser non-grain crop material such as stalks and leaves are transported to the rear of the combine through a chopper assembly and discharged back to the field using a spreader system. The separated grain, together with some finer non-grain crop material such as chaff, dust, straw, and other crop residue are discharged through the concaves and fall onto a grain pan where they are transported to a cleaning system. Alternatively, the grain and finer non-grain crop material may also fall directly onto the cleaning system itself.
After passing through the threshing and separating system, the coarse non-grain crop material can flow into a chopper assembly to be cut into finer pieces before being spread on the field. Chopping the non-grain crop material into finer pieces increases the surface area of the crop material, allowing for quicker decomposition. One type of chopper assembly that is commonly employed has multiple moving knives that cooperate with stationary counter knives to chop the crop material into finer pieces. A shear bar can also be placed after the stationary counter knives to impede the flow of the crop material through the chopper assembly and increase the chop quality.
In certain cases, the user may not want the crop material that passes through the chopper assembly to be cut into finer pieces. In such instances, the user can switch the chopper assembly from a chopping mode where the counter knives are raised to cooperate with the moving knives to chop the crop material and a disengaged mode where the counter knives are lowered so that the counter knives do not cooperate with the moving knives. When the counter knives are lowered, the moving knives simply push any contacted crop material toward the rear of the combine with minimal chopping. However, the shear bar is typically bolted in the chopper assembly and does not lower when the counter knives are placed in the disengaged mode. As such, the shear bar can unnecessarily impede crop material flow through the chopper assembly in disengaged mode and provide resistance that causes chopping of the crop material when no chopping is desired.
What is needed in the art is a chopper assembly that can overcome some of the previously described disadvantages of the prior art.